The invention involves a method and apparatus for applying glue to sheet products, such as envelopes, card stock and other flat products. More particularly, the invention involves the simultaneous application of glue to opposed ends of the sheet products.
In the production of sheet products, such as card stock and other paper products, there are many instances when the product is to be folded, and glue is applied to the flaps so as to seal the various panels and flaps together. An example of this is in the production of envelopes, some of which require the application of glue to more than one flap of the folded product.
The conventional approach for the application of glue in an automated glue applicator machine is to feed a plurality of identical sheet products in sequence to a conveyor system. The conveyor system advances each product in spaced relationship along a processing path by controlling one end of the product while applying glue to the other end of the product. Typically, drive belts must carefully control each product so that the glue is properly applied at the precise location on the sheet product. In some instances, the glue, such as latex and remoistenable glues, are dried as the products are advanced farther along the processing path. In other instances, the glue is covered with a peel-away seal strip that can be removed from the sheet product when the panel is to be adhered to an adjacent surface.
When applying glue to the closure flaps of a series of envelopes, the typical approach is to advance the envelopes along a processing path with the fold of the flap extending parallel to the direction of movement, and with the flap folded closed as it approaches the processing path. A flap opener, in the shape of a small plow, is positioned in the path of the flap and the flap opener engages and opens the flap so as to place it in the proper path for receiving the glue. The flap opener, the gum box, the glue applicator drum and a heater that dries the adhesive after the adhesive has been applied to the envelope are all on the operator""s side of the machine. The other side of the machine typically includes overlying conveyor belts that grip and advance the envelopes through the workstations along the processing path.
In those instances where glue is to be applied to both ends of a sheet product, it is customary to run the sheet product through the glue applicator twice, with the first run applying glue to one end, and then reversing the product for the second run so that the same system applies glue to the other end of the sheet product.
When the sheet product must be run through the glue applicator twice in order to apply glue to the opposed ends of the sheet product, the expense of the product increases because of the additional machine time required for the second run, and because of the extra handling and planning required by the machine operator.
In those instances where attempts are made to apply glue to both ends of the sheet products with one run through the glue applicator system, the glue applicator drum can be set up with its glue applicator strips spaced about the circumference of the cylindrical surface instead of along the length of the cylindrical surface. The glue transfer strips are positioned so as to apply glue to both ends of the sheet products during a single run; however, since the transport belts must engage at least an edge portion of the sheet products, the glue can be applied only to approximately one-half the width of the sheet products, leaving the remaining portion of the sheet product available for engagement by the transport belts. In many cases, the products of this process are unacceptable to the purchaser since the glue is not applied across the entire ends of the sheet product.
It is to the above noted concerns that this invention is directed.
Briefly described, the present invention includes a method and apparatus for simultaneously applying glue to both ends of a sheet product, drying the glue, and shingle stacking or vertical stacking the sheet products for packaging and delivery to a purchaser.
An examples of the sheet products to which the glue is to be applied can include hanger tags for coat hangers, envelopes, and virtually any card stock or other paper products or even other sheet material that has enough body strength and weight to be advanced with its body extending parallel to the direction of advancement through the system without inadvertently folding or wrinkling.
The sheet products are arranged in stacked relationship and are fed to the system by a feed wheel of conventional design. Each sheet product is deposited by the feed wheel onto an aligner conveyor that is a conventional surface conveyor having spacer pins protruding therefrom for engaging the rear edge of each product, for assuring that the trailing edge of each product is properly positioned as the product advances on through the processing path. The products are moved in sequence from the aligner section onto a vacuum surface conveyor belt where a partial vacuum beneath the belt holds each sheet product in place as the sheet products advance with the belt beneath a glue applicator drum. A gum box of conventional construction applies liquid glue to the applicator pads that are carried by the cylindrical surface of the glue applicator drum, and the applicator pads rotate into contact with the sheet product and transfer the glue to the sheet product.
The sheet products continue to move beyond the glue applicator drum on the vacuum conveyor and the vacuum conveyor delivers the sheet products to dryer belts.
The dryer belts are a pair of overlying endless conveyor belts that grasp each sheet product in sequence and move the sheet products along a drying path where heated air is directed toward the glue and dries the glue.
A feature of the invention is that the glue applicator drum can be as long as the width of the machine and can apply glue to the opposed ends of the largest sheet products that can be processed through the machine. For example, the sheet product being run through the system might be card stock and it is desirable to apply glue simultaneously to both ends of the card stock. The glue transfer pads are located on the glue applicator drum in spaced relationship along the length of the cylindrical surface of the drum. The sheet products are oriented with their ends aligned across the processing path so as to accept stripes of glue at their ends from the glue transfer pads. This leaves a space on the card stock between the stripes of glue where glue has not been applied to the card stock that is later used as a belt engaging space. This space is later engaged by the overlying dryer belts that grasp the card stock without contacting the glue and continue to advance the card stock through the system.
Heated air is applied in straddling relationship with respect to the dryer belts, in the paths where the glue of the card stock will travel. Typically, the heaters comprise separate ducts that extend in straddling relationship beside the dryer belts. Blowers and induction heaters are mounted at one end of the heater ducts for supplying warm air through the ducts, and the ducts have exhaust ports at intervals along their lengths that are directed toward the paths that are to be traveled by the glue applied to the card stock.
Another feature of the invention is that the transfer strips that are carried by the cylindrical surface of the glue applicator drum can be of virtually any shape and size that is compatible with the shape and size of the work pieces to be processed through the system, including having transfer strips at only one end of the glue applicator drum. This latter configuration makes the system compatible for applying glue to only one end of a sheet product, or to only the other end of the sheet product. For example, there are some instances when glue is to be applied to the flaps of envelopes. In this situation, the glue applicator strips would be located at one end of the glue applicator drum, but the other end of the drum would be left blank. However, some envelopes are considered to be xe2x80x9cleft-handedxe2x80x9d or xe2x80x9cright-handed,xe2x80x9d in that the flap to which the glue is to be applied must be run on the left-hand side of the system, or on the right-hand side of the system, usually dependent upon the way that the seams are formed in the envelope. The invention disclosed herein is compatible with operating the envelopes in either a xe2x80x9cleft-handedxe2x80x9d or xe2x80x9cright-handedxe2x80x9d orientation, by simply adjusting the placement of the glue applicator strips on the glue applicator drum.
Another feature of the invention is the separate heaters used to apply hot air to the glue, to dry the glue. If only one end of the sheet product is to receive glue, only one heater may be activated, thereby conserving the energy of the inactive heater.
Therefore, it is an object of this invention to provide an improved, multi-purpose glue applicator for sheet products, such as envelopes, card stock, and other paper products, which is more versatile in that it can apply glue to various configured sheet products, and which tends to avoid the need for advancing the sheet products more than once through the machine for application of glue to different surfaces of the sheet products.
Another object of the invention is to provide an improved glue applicator for sheet products which has the capacity of applying glue simultaneously to opposed ends of the sheet products.
Another object of the invention is to provide an improved glue applicator for sheet products that includes the ability to apply glue to one end, or to the other end, or to both ends of a sheet product, and then to dry only those ends of the sheet product to which glue has been applied.
Other objects, features and advantages of the present invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawings.